Method for explosion reticulation using a non-inflammable liquid



Jan. 10, 1967 .w. MEISEL, JR. ETAL 3,

METHOD FOR EXPLOSION RETICULATION USING A NON-INFLAMMABLE LIQUID Filed Jan. 27, 1964 POLYMERIC FOAM MATERIAL WETTED WITH A NON-IGNITABLE LIQUID POLYMERIC FOAM MATERIAL F INTRODUCED TO A CONFINED zoNE INTRODUCING A MIXTURE OF OXYGEN- CONTAINING GAS AND A GAS EXPLOSIVELY COMBUSTIBLE IN CONTACT WITH OXYGEN EVACUATING THE GAS FROM THE CONFINED ZONE INTRODUCING A LIQUID FUEL WITHOUT BRINGING IT INTO CONTACT WITH THE FOAM BODY, WHICH FLUID HAS A HIGH VAPOR PRESSURE AT STANDARD CONDITIONS KNEADING THE FOAM MATERIAL TO INSURE DISTRIBUTION OF THE LIQUID MAINTAINING THE TEMPERATURE OF AND EXPLOS'VE GAS M'XTURE THE ZONE AT A LEVEL AT WHICH THE FUEL HAS A GAS PHASE EXPLODABLE WITH OXYGEN INTRODUCING A MIXTURE OF OXYGEN-CONTAINING GAS TO THE ZONE PERMEATING THE FOAM MATERIAL WITH THE RESULTING GASEOUS MIXTURE IGNITING THE GAS MIXTURE TO OBTAIN A FLAME PROPAGATION RECOVERING A RETICULATED POLYMERIC FOAM MATERIAL.

INVENTORS. FRED W. MEISEL, JR

EDGAR ALLAN BLAIR BY Z/ ATTORNEY United States Patent i 3,297,803 METHOD F OR EXPLOSION RETICULATION USING A NON-INFLAMMABLE LIQUID Fred W. Meisel, Jr., Media, and Edgar Allan Blair, Swarthmore, Pa., assignors to Scott Paper Company, Philadelphia, Pa., a corporation of Pennsylvania Filed Jan. 27, 1964, Ser. No. 340,487 15 Claims. (Cl. 264-84) This invention relates to an improved method for treating polymeric foam bodies, more particularly, this invention pertains to reticulation and modification of polymeric foam materials susceptible of undesired changes under explosion reticulation conditions.

Prior art processes for treating foams by explosion techniques have been disclosed in Serial No. 324,578, filed November 18, 1963. Foams represented therein give heretofore unachieved properties although they are in many respect similar to those disclosed in Serial No. 655,368, filed April 26, 1957 and now abandoned. Both of the above-referenced applications are assigned to a common assignee, Scott Paper Company, which is also the assignee of the present application. While the above flame reticulation process represents a significant breakthrough in using an alternative process for foam reticulation, the present process illustrates a further improvement over the flame or explosion process shown in the firstmentioned case.

It has been observed that when certain polymeric, organic foams are subjected to the de'win-dowing explosion, the foam bodies tend to tear or shatter as well as burn on the surface.

Under proper conditions, the tearing and shattering can be controlled, but it renders the prior art explosive process more cumbersome to use. Decreasing the explosive force by adding more nitrogen generally does not solve the problem under all conditions as the explosion then fails to dewindow the diaphanous faces of foam polyhedrons. Increasing the amount of fuel in the explodable gas mixture, on the other hand, often results in burning. Soft foams or foams which melt easily are especially susceptible to slight variations from the ideal condition. For better understanding of this process the general teaching of the prior art process disclosed in the above Serial No. 324,578 is incorporated herein.

It has now been found that the explosive force results in an improved process over that in Serial No. 324,578 if the process is modified to maintain the brisance needed to deWindoW the materials and, at the same time, the brisanse is specifically minimized to eliminate the tearing and shattering of the foam. Thus, a novel explosion process is obtained providing exceptionally good controls.

The invention has been accomplished by running the process as in Serial No. 324,578 except that the foam body is soaked in a nonflammable, or nonignita'ble liquid capable of absorbing the excessive explosive force. Water is the preferred liquid. Others are the fire-resistant hydraulic oils made of monomeric and polymeric phosphorous or silicone derivatives. Mixtures of the above liquids, if compatible, serve equally well. Other nonflammable liquids are obvious to a man skilled in the art. Organic, polymeric foams such as polyurethane, polyvinyl, polyolefin (ethylene), etc. are specific examples within the scope of this invention.

The invention disclosed herein accomplished by a process for reticulating noninflammable liquid-fluid containing open-celled, organic, polymeric foams comprising the steps of: (a) introducing into a gas-confining, foam-containing zone a mixture of oxygen-containing gas and a gas explosively combustible in contact with oxygen; (b) permeating the previously wetted foam material with said process employing the present invention.

Patented Jan. I0, 1967 gas composition for a time suflicient to insure a distribution of sufficient quantity of the gas mixture in the foam material; (c) igniting the gas mixture to obtain a flame propagation throughout the wetted foam material; and (d) recovering a reticulated foam material. In general, the above foam will contain from about 6 to about 125 p.p.i.; in the preferred embodiment, of from about 10 to about p.p.i.; or, in the more preferred embodiment, 10 to 45 p.p.i.

In another aspect, this invention is accomplished by a process for dewindowing a polyurethane foam material having p-artially-communicating cells comprising the steps of: (a) introducing into a gas-confinin foam containing zone a foam material wetted with a nonignitable liquid, (b) thereafter introducing in said zone a mixture of oxygen-containing gas and a gas explosively combustible in contact with oxygen; (0) permeating the foam material with said gas composition for a time sufficient to insure a distribution of suificient quantity of the gas mixture in the foam material; (d) igniting the gas mixture to obtain a flame propagation throughout the wetted foam material; and (e) recovering a reticulated foam material.

In a further aspect, this invention has been accomplished by a process for preparing reticulated, organic, polymeric foam body having a three-dimensional strand network joined at the nexuses 'wherein the strands define the polygonal faces of a foam buildingblock polyhedron, said polyhedron having a majority, but less than all of the faces defined by said strand network, and a unitary membrane joined to the defining strands, said individual polyhedrons joined together by common nexuses and strands making up the foam body, wherein the mebraneless faces are in open communication with other cells open faces, said body containing a dispersed liquid fl-uid substantially nonignitable under explosive flame conditions, the process comprising the steps of (a) introducing into a [gas-confining zone the fluid-containing body; (b) permeating the gas and foam-body confining zone by introducing into said zone a mixture of oxygen-containing gas and a gas explosively combustible in contact with oxygen, the amount of oxygen in the mixture being in excess of at least that amount of oxygen introduced in the mixture in the form of air; (0) kneading said foam material to insure a further distribution of said fluid and explosive gas mixture; (d) igniting the (gas mixture to obtain a flame propagation in the foam material (e) recovering a reticulated foam material and (f) repeatedly subjecting the foam material to said modified explosive treatment.

In still another aspect, this invention has been accomplished by a process for producing a membrane-free foam body comprising the steps of (a) introducing into a gasconfinin-g zone a foam body containing a liquid fluid noninflammable under explosive flame conditions; (b) evacuating the gas-confining, foam-body containing zone; (c) introducing into the gas-confining zone a liquid fuel without bringing said liquid fuel in contact with said liquid fluid-containing foam body, said liquid fuel being characterized by a high vapor pressure at standard conditions; (d) maintaining the temperature in the confined zone at a suitable level at which the vapor pressure of the liquid fuel is suflicient to permit the fuel to exist in gas phase to form an explodable mixture in the presence of oxygen; (e) introducing a mixture of oxygen-containing gas into said gas-confining zone; (f) permeating said foam body with the oxygen-containing gas and vapor from the evaporating liquid; (g) igniting said combustible mixture; and (h) recovering the foam material.

In the drawing, FIGURE 1 diagrammatically represents an illustrative process and several variations of the FIGURE 2 is a greatly enlarged perspective View of an individual polymeric foam cell illustrating the skeletal structure and remaining cell membranes. FIGURE 3 is a greatly enlarged perspective view of an individual reticulated polymeric foam cell illustrating the skeletal structure The bag may also be connected to a vacuum source to evacuate air from the foam. Repeating the evacuating operation a few times insures the ready distribution of the explosive gas.

shown in FIGURE 2 which remains after the removal of The following examples are included to illustrate the the cell membranes in accordance with the process of the various facets of the invention. These examples are to invention. be construed with reference to the above discussion and The novel aspect of controlling the reticulation is acclaims, and are not intended to limit the broader scope complished by the above process wherein said liquid, beof the invention. ing selected from at least one member of the group con- EXAMPLE 1 sisting of lower alkyl ethers of from 1 to 4 carbon atoms, A block of flexible polymeric polyether polyurethane at least one of the alkyls having 2-carbon atoms when the having a density of L0 Pci and 45 p.pj' (pores per other alkyl lOwer alkyl aicohols of from 1 to 4 inch), made by reacting a mixture of polyether triol and carbon atoms, 531d compounds being further character diol with toluene diisocyanate and water in a conventional iZed y high P M65511res at normal Conditions- A 15 one-shot process, but obtaining a part of the blowing with successful reticulation is characterized by the fact that F 11, i t t d according to the procedure outthe diaphanous membranes of said foam material are lined above (also described in Serial No. 324,578) with sent from the final product in the areas of the exposive several fuel gases. effect. Results:

Gas comp, 1 vol. Comp/Dell.

percent Foam Tens., E]ong., Tear, Comp. Run Fuel wt. loss, p.si percent lbs/in. Set Reticulation percent 0: Fuel 50% 66% 1 Pre ene 63 7 4.8 19.1 400 2.7 26 .12 .12 .16 Complete. 2. Acetylene 37 15 2.0 13.9 315 2.0 20 .17 .20 .27 Do.

3 -do 70 15 6.0 16.0 380 2.4 24 .12 .14 .17 Do. Control 9.9 165 1.3 11 .29 .30 .37 None.

1 Balance N2.

In order to aid the interconnection of the cells, the Foam properties are determined in all examples by membranes may also be mechanically ruptured without ASTM Methods Dl564-54T. removing them, such as by wringing or swelling the foam in a solvent and then breaking the weakened foam. Still EXAMPLE 2 other methods may be used to rupture the membranes 45 A block of polymeric polyether polyurethane a (without being removed from the foam body), but this generally similar to the material of Example 1 is used, step is generally for the purpose of enabling ready perexcept that a different polyether is employed. This polymeating of the water or the noninflammable fluid and the ether is obtained from Witco Chemical Co., Chicago, Ill. explosive gas mixture. and is sold under the trade-mark Formez G-26-9 and Various gases are useful as the explosive (combustion) is characterized by an hydroxyl number of about 110 with force. Acetylene and propane are the preferred gases. an acid number of about 0.06 and an unsaturated milli- Other gases suitable for the present process are selected equivalent per gram of 0.006, and is treated according to from at least one member of the group methane, ethane, the procedure of Example 1. Density of the foam is butane, ethylene-in general exemplifying the hydrocar- 1.02; pore size is p.p.i.

Gas comp., 1 vol. Comp/Dell.

percent Foam Tens Elong., Tear, Comp. Run Fuel wt. loss, p.s.1 percent lbs/in. Set Reticulation percent 0, Fuel 25% 05% iiz i fiieiil 1 3.2 iso 240 1.8 (2) 10 10 .12 .22 if do 70 15 22.7 305 2.1 19 .00 .07 .12 Do.

6.5 155 1.3 13 .11 .14 .21 None.

1 Balance Ni. 1 Sample torn apart. 3 Sample torn.

bon group-as well as the above-mentioned acetylene This is very soft foam and considerable difficulty with and propane. Other materials useful in the reaction are tearing is encountered; otherwise, results are generally hydrogen, hydrogen sulfide, ethylene oxide, methylether, similar to those obtained with the foam of Example 1. and liquids, such as methylethylether, the low-boilingpoint alkyl ethers, and alcohols such as methyl, ethyl and E A 3 isopropyl alcohol.

Gases used in the explosion are controlled as to their A block of flexible polyurethane adipate polyester foam ratios and rate by gauges and fiowmeters located at sup- Of a density of 1.9 pounds per cubic foot and of 45 p.p.i. ply sources. Generally, the supply sources are suflicientis wetted with water. A portion of the wet block is exly far removed from the explosion zone. posed to conditions created by exploding a gaseous mix- The explosive zone to which the gases are fed via the ture of acetylene and oxygen of 1 part acetylene t0 2 and supply line, consists of a polyethylene bag containing a 2.5 parts of oxygen and fed to thesystern at a rate of 35 foam block and an ignition source to initiate the ex cubic feet per minute for 3 minutes. The foam is effecplosion, tively reticulated without the surface scorching obtained when the foam is subjected to the explosive force in the dry state under the same conditions.

EXAMPLE 4 6 Above experiments are then carried out by wetting the foam sample with water. Rupturing or tearing is avoided and burning eliminated if the foam block is Wetted enough to absorb the excess energy. This example demonstrates Blocks of unreticulate foams which are of the same 5 that highly hrisaht explosion Such as Obtained y a block as in Example 2 are subjected to the same explosion 5050 IIliXtllre 0f the above g components y effectreatment except that the foam is immersed in water, tively be modified by using water as energy-dissipating squeezed to remove excess water and then reticulated. m

The foam bodies, when treated with explosive flame di Foams treated under the conditions employed above inplay substantially no tearing, 10 clude the previously mentioned ethers, esters and castor oil foams. By means of this modified procedure rigid EXAMPLE 5 polyether foams have also been successfully reticulated.

A large blo k of polyurethane foam i prepared b a In practicing the invention foams of various pore size conventional one-shot foaming process using an 8020 pp y t explosloh trfiatfheht 0f fOaITlS h isomeric mixture of 2,4- and 2,6-toluene diisocyanate and 15 dlfferent P SlZeS generally l'eqlllres some l Castor iL ment in the fuel-gas, oxygen-containing gas and water Specimens of X X 3" are cut from h large l k variables. From a practical point of View the first two and exposed to conditions created by igniting an explosive Vaflahles r t p d o See if the deslred c ntrol mixture of acetylene and oxygen. An effectively reticucan be f y a d; then, if the first two variables do lated foam is obtained; however, it is somewhat soft and 20 not readily glVe the desired result the molstenlng p '1 gummy Wetting another pecimen of The san' e foam used to achieve better COIltIOl. HOWBVEI, it is to be underwith water and then subjecting it to an exploding acetyl- Stood t using the I10h1hfllmmah1e fluid at y h ene-oxygen mixture id bl di i i h th icondition affords more precise process control and faclliness of h f tates the determination of the optimum conditions,

EXAMPLE 6 What iS claimed is! 1. A process for removing diaphanous membranes A number of specimens from a p.p.i. polyurethane from organic, polymeric foams capable of being peradipate polyester foam are subjected to an explosive force meated with an explodable mixture of fuel gas and oxygene-rated by hydrogen sulfide oxygen-nitrogen mixture. gen comprising the steps of:

The data below illustrate the results. 30 (a) applying a dispersed noninflammable fluid to the HYDROGEN SULFIDE Gas mixture, vol. percent Total gas Orig. wt, Wt. after Run flow rate, grams treatment, Rctic.

o.f.h. grams H25 02 N2 0 7. 5 53. 6 52.8 Compl. 0 10. 0 52. 3 51. 0 Compl. 0 13.0 51. 1 50. 3 Comp]. 0 l0. 0 52. 5 52. 2 Incompl. 0 10.0 50.6 Complete;

specimen burned.

The above experiments are then carried out by slightly internal and external surfaces of said foam body; wetting the specimens. If excess water (after dipping and (b) introducing said explodable fuel-oxygen mixture slight squeezing) is present the explosion is considerably into said foam body; less effective. This indicates that Water iS a gOOd fluid (c) creating an explosive flame propagation in the foam for modifying the explosive force used in foam reticulamateri l; a d tion. ((1) recovering the product.

EXAMPLE 7 2. A process for reticulating open-celled, organic, poly- A number of specimens from a 45 p.p.i. polyurethane mhnc foamsfomprhsmg the p? of! adipate polyester foam are subjected to an explosive force apply'lhg a dlspersed nohlhflammahle hquld fl111d generated by ethylene oxide-oxygen mixture according to to the Int rnal and Xternal Surfaces of a body of the procedure described above. The data below illustrate penelled, organic, polymeric foam material; the results. (b) introducing a mixture of oxygen-containing gas and ETHYLENE OXIDE Gas Mixture, vol. percent Total gas Orig. wt., Run flowf gate, grams Comments 0. E.O 02 N2 100 0 0 5 50.3 No explosion.

28. 5 71. 5 0 17. 5 50. 5 Bad rupture; complete reticulation. 20.0 0 2. 5 49. 7 Very slight explosion; burning. 10.0 90.0 0 50 52.4 No explosion. 50.0 50.0 0 10 52.3 Bad rupture; complete reticulation. 75.0 25.0 0 10. 5 53.0 Burning; incomplete reticulation. 28.5 71.5 0 17.5 51.2 Explosion veryloud; complete reticulation. 30.0 50.0 0 10 51.3 Very loud explosion (brisant); complete reticulation; tearing.

a gas explosively combustible in contact with oxygen into a gas-confining zone;

() permeating the previously wetted foam material with said gas composition for a time suflicient to insure a distribution of the gas mixture in the foam material;

(d) igniting the gas mixture to obtain a flame propagation in the foam material; and

(e) recovering a reticulated foam material.

3. A process for flame dewindowing of organic, polymeric foam material having partially communicating cells comprising the steps of:

(a) applying a dispersed noninflammable liquid fluid to the internal and external surfaces of a body of said foam;

(b) introducing said body of foam material and a mixture of oxygen-containing gas, into a gas-confining zone, and thereafter introducing into the same zone a gas explosively combustible in contact with oxygen, the amount of oxygen present being in excess of at least about that amount of oxygen introduced in the mixture in form of air;

(c) permeating the foam material with said gas composition for a time suflicient to insure a distribution of the explosive gas in the foam material;

(d) igniting the gas mixture to obtain an explosive reaction of the oxygen and combustible gas in the gasconfining zone; and

(e) recovering a reticulated foam material.

4. A process for dewindowing polyurethane foam material having partially communicating cells comprising the steps of:

(a) applying a dispersed noninflammable liquid fluid to the internal and external surfaces of a body of polyurethane foam material;

(b) introducing the wetted foam material and a mixture of oxygen-containing gas and a gas explosively combustible in contact with oxygen into a gas-confining zone;

(c) permeating the foam material with said gas composition for a time suflicient to insure a distribution of the gas mixture in the foam material;

(d) igniting the gas mixture to obtain a flame propagation in the foam material and;

(e) recovering a reticulated foam material.

5. The process according to claim 4 wherein the foam material is polyurethane polyester foam.

6. The process according to claim 4 wherein the foam material is polyurethane polyether foam.

7. The process according to claim 2 wherein the wetted foam material is a polyvinylchloride.

8. A process for preparing reticulated, organic, polymeric foam from a foam body having a three-dimensional strand network joined at the nexuses wherein the strands define the polygonal faces of an individual foam building block polyhedron, said polyhedron having a majority but less than all of the faces defined by said strand network and a unitary membrane joined to the defining strands, said individual polyhedrons joined together by common nexuses and strands making up the foam body, wherein the membraneless faces are in open communication with other cells open faces, the process comprising the steps of:

(a) applying a dispersed noninflammable liquid fluid to the internal and external surfaces of said foam body;

(b) introducing into a gas-confining zone said fluidcontaining body;

(0) permeating the gasand foam body-confining zone by introducing into said zone a mixture of oxygencontaining gas and a gas explosively combustible in contact with oxygen;

(d) kneading said foam material to insure a further distribution of said fluid and explosive gas mixture;

(e) igniting the gas mixture to obtain a flame propagation throughout the foam material; and

(f) recovering a reticulated foam material; and

(g) repeatedly subjecting the foam material to said explosive treatment.

9. A process for producing a membrane-free organic,

polymeric foam body comprising the steps of:

(a) applying a dispersed noninflammable liquid fluid to the internal and external surfaces of a body of open-celled, organic, polymeric foam materials;

(b) introducing into a gas-confining zone a foam body containing a liquid fluid non-inflammable under explosive flame conditions;

(0) evacuating gas-confining foam body-containing zone;

((1) introducing into the gas-confining zone a liquid without bringing said liquid in contact with said foam body, said liquid fuel being characterized by a high vapor pressure standard conditions; 1

(e) maintaining the temperature in the confined zone at a suitable level at which the vapor pressure of the liquid fuel is suflicient to permit the fuel to exist in gas phase at a concentration to form an explosive mixture in the presence of oxygen;

(f) introducing a mixture of oxygen-containing gas into said gas-confining zone;

(g) permeating said foam body with the oxygen-eon- 'taining gas and vapor from the evaporating liquid;

(h) igniting said combustible mixture; and

(i) recovering the foam material.

10. An improved process for producing reticulated, organic, polymeric foam materials comprising the steps of:

(a) taking an open-celled foam of from 6 to pores per linear inch and wetting it throughout with water;

(b) evacuating a gas-confining and wet foam materialcontaining zone;

(c) introducing into the evacuated gas-confining zone a mixture of oxygen-enriched gas and a gas explosively combustible in contact with oxygen, said combustible gas being selected from at least one member of the group consisting of hydrogen, hydrogen sulfide, acetylene, ethylene, methane, ethane, propane, utane ethylene oxide and methylether;

(d) permeating said foam material with said explosive gas mixture;

(e) igniting said gas mixture; and

(f) recovering a reticulated product.

11. The process according to claim 10 wherein the gas is acetylene and the foam material is polyether polyurethane.

12. The process according to claim 10 wherein the gas is ethylene oxide.

13. A process for producing reticulated foam materials comprising the steps of:

(a) taking an open-celled foam of from 6 to 125 pores per linear inch and wetting it throughout with Water;

(b) evacuating a gas-confining and wet foam materialcontaining zone;

(c) introducing into the gas-confining zone a liquid Without bringing said liquid in contact with said foam body, said liquid being selected from at least one member from the group consisting of lower alkylethers of from 1 to 4 carbon atoms, at least one of the alkyls having 2 carbon atoms when the other is CH and lower alkyl alcohols, said compounds being further characterized by high vapor pressures at normal conditions;

((1) maintaining the temperature in the confined zone at a suitable level at which the vapor pressure of the liquid fuel is sufficient to permit the fuel to exist in gas phase in a concentration to form an explosive mixture in the presence of oxygen; but at a temperature lower than the boiling point of water;

(e) introducing a mixture of oxygen-containing gas into said liquid and gas-confining zone;

9 10 (f) permeating said foam body with the oxygen-con- 15. The process according to claim 14 wherein the taining gas and vapor from the evaporating liquid; liquid is isopropylalcoh-ol.

(g) igniting said combustible mixture, said oxygen- References Cited'by the Ex er vapor mixture being characterized by a flame front capable of reticulating the diaphanous membranes of 5 2 961 710 PATENTS 264-54 said foam material; and ar (h) recovering the foam material 3,175,025 3/1965 Geen et a1 264--321 XR 14. The process according to claim 13 wherein the ALEXANDER BRODMERKEL Primary Examiner liquid is methylethylether. P. E. ANDERSON, Assistant Examiner. 

1. A PROCESS FOR REMOVING DIAPHANOUS MEMBRANES FROM ORGANIC, POLYMERIC FOAMS CAPABLE OF BEING PERMEATED WITH AN EXPLODABLE MIXTURE OF FUEL GAS AND OXYGEN COMPRISING THE STEPS OF: (A) APPLYING A DISPERSED NONINFLAMMABLE FLUID TO THE INTERNAL AND EXTERNAL SURFACES OF SAID FOAM BODY; (B) INTRODUCING SAID EXPLODABLE FUEL-OXYGEN MIXTURE INTO SAID FOAM BODY; (C) CREATING AN EXPLOSIVE FLAME PROPAGATION IN THE FOAM MATERIAL; AND (D) RECOVERING THE PRODUCT. 